THE RELATIVE TROUGH FROUDE NUMBER FOR TERMINATION OF WAVE BREAKING

摘要

Wave breaking termination is an important boundary for the determination of the wave breaking area especially when termination occurs in the middle of the domain, such as on a bar-trough shaped beach. However, this subject has not been closely examined. The development of a wave breaking index based on more experimental and theoretical evidence is needed. The Relative Trough Froude Number (RTFN) is a wave breaking index based on the moving hydraulic jump concept. The critical condition for wave breaking termination was determined from wave tank experiments on a horizontal bottom as 1.15 (Okamoto and Basco, 2004). In this paper, we examine two issues related to the termination condition of wave breaking (1) how the RTFN and other wave breaking indices approach the termination condition on a horizontal bottom, and (2) the bottom slope influence on the termination condition. The RTFN approaches the termination condition at a slower rate than the other indices based on free surface geometry so that the index value stays noticeably higher than the critical condition during wave breaking. Wave properties in the trough area show different patterns from the one obtained on a horizontal bottom. By using two hypothesizes, the RTFN at the "termination" location comes close to the theoretical value, but further investigation is required.